Finished gemstones which are available to a consumer are cut from a rough gemstone. In order to determine the optimal way to cut or saw the rough gemstone, it must first be inspected.
This inspection may be done by a trained professional, who then marks the rough gemstone with sawing line(s) to indicate to a stonecutter how to form one or more finished stones from the rough stone.
Alternatively, systems have been developed to automatically inspect and mark sawing lines on the rough stones. These systems typically first map the rough stone to determine its shape, then determine how to best cut it, and finally mark a sawing line thereon. One example of such a mapping and marking system is DiaMark™ produced by Sarin, Technologies Ltd, Ramat Gan, Israel.
In the latter type of system, a gemstone to be mapped is rotated, its three dimentional silhouette is determined, and its surface is imaged, at a plurality of angular positions of the stone, whereby the shape of the stone is determined including concavities on its surface.
One way of mapping a gemstone is described in the Applicant's U.S. Pat. No. 6,567,156, where in order to determine concavities on the surface of a gemstone, structured light triangulation is used, in which a laser beam is directed at the stone at various angular positions thereof, its reflection captured and compared to the reflection that would be received from a hypothetical gemstone having the same 3-D silhouette. Defects and concavities are indicated by deviations of the captured reflection from that which would be detected from the hypothetical gemstone.